This is a bad idea. There is very little dragon fluff to the Sorcerer. There is one line, which is then handwaved away as "boasts" in the next sentence. Making an entire class' powers based from exceptional heritage makes other classes with greater heritage seem silly (how is a half-dragon fighter weaker than a Sorcerer with forced draconic heritage? After all he's got much more dragon in him, he should be able to everything the sorcerer can and more).
You could also ask why the 36 HD great wyrm white dragon is only as good as the 13 HD sorcerer. That's just the way it works.
Sarah, human gestalt druid/totemist Adrian, human rogue Calypso, half-nymph human gestalt druid/miscellaneous